JP3406889B2 - Distance measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device used in a device for measuring the shape of the surface of a subject and measuring the distance from a reference point to the surface of the subject.

[0002]

2. Description of the Related Art A capacitance type gap sensor for measuring a gap between a surface of a subject and an electrode by detecting a capacitance between a subject surface of a conductor and an objective electrode facing the surface. It has been known. This type of sensor has higher accuracy and reliability and a longer life than other optical, electromagnetic (eddy current) and air type gap sensors. Also,
Responsiveness is also good.

[0003]

However, in the capacitance type sensor, the gap between the measured object surface and the object surface is an average value over the entire surface of the objective electrode. Therefore, the area of the objective electrode cannot be so large. If this area is small, there is a problem that the effective measurement range is limited to a narrow range. For example, when measuring the surface shape with an accuracy of about nanometer, the measurement range is limited to about 100 μm or less. A special device is required to position the objective electrode in such a narrow range, and skill is required for the work.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a distance measuring device having a wide measuring range.

[0005]

In order to solve the above-mentioned problems , a distance measuring apparatus according to the present invention comprises a frame, an objective electrode arranged with a gap from the surface of a subject, and the objective electrode. Objective electrode supporting means for supporting the frame so that the gap with the surface of the subject is within a predetermined range , objective electrode displacement detecting means for detecting the displacement of the objective electrode with respect to the frame, and the objective electrode and the surface of the subject. Gap detection means for detecting these gaps based on electrostatic capacitance, and distance calculation means for calculating the distance from a predetermined point on the frame to the surface of the subject based on the displacement of the objective electrode and the gap. is doing.

With this configuration, the objective electrode having a narrow measurement range but high accuracy is held by the objective electrode support means at a position where the gap of the object to be measured falls within the measurement range. On the other hand, the displacement of the surface of the subject that exceeds the measurement range of the objective electrode is measured by using the objective electrode displacement detecting means together.

Furthermore, the objective electrode support means, the controlled based on the detected value of the gap detection means, the detection value prior to
It can be assumed to have a driving means for driving the objective electrode as serial a predetermined range. Further, the objective electrode supporting means may have a biasing means for biasing the objective electrode toward the neutral position.

More specifically, the objective electrode supporting means holds the objective electrode at one end, is arranged in a direction substantially perpendicular to the surface of the subject, and a rod movable in this direction,
A linear motor including a permanent magnet fixed to the rod and a coil fixed to the frame, a support mechanism that movably supports the rod with respect to the frame, the detected objective electrode, and the surface of the subject. And a motor drive unit that controls the linear motor based on the gap. Furthermore, the frame includes a tubular member that surrounds at least a part of the rod and is disposed substantially coaxially with the rod, the coil is disposed on the tubular member, and the support mechanism includes the rod and the tubular member. It may be arranged in between.

Further, the objective electrode displacement detecting means includes an electrode fixed to the frame and an electrode fixed to the rod, and detects a change in distance between the two types of electrodes as the rod moves. Thus, the displacement of the objective electrode can be detected. Alternatively, the displacement of the objective electrode may be detected by detecting the change in the area of the facing portion of the two types of electrodes as the rod moves.

Furthermore, a linear scale having a scale that moves in relation to the displacement of the objective electrode and a scale detection unit that is fixed to the frame side and monitors the passing scale, or a laser interferometer. You can also

Further, the support mechanism may be arranged between an outer flange projecting outward from the rod and an inner flange projecting inside the tubular member, and the structure thereof is the inner and outer flanges. A supporting leg including two plates arranged in series between the two plates, two plates, one plate and an outer flange, and an elastic hinge arranged between the other plate and the inner flange. It may include at least three legs.

Furthermore, the support mechanism may be a static pressure gas bearing.

It is possible to measure the surface shape by using the above distance measuring device. That is, it is possible to move the frame within a predetermined plane, obtain measurement values of the distance measuring device at a plurality of movement points of the frame, and calculate the shape of the subject surface based on the measurement values.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a distance measuring device 10 of this embodiment. The objective electrode 14 facing the subject surface 12 is fixed to the tip of a rod 16 of a substantially cylindrical or circular tube.
The rod 16 is supported by a tubular frame 20 via support structures 18 arranged at two axial positions thereof. The support structure 18 maintains the rod 16 in the neutral position by elastic force. That is, when the rod 16 is displaced with respect to the neutral position, the elastic force acts toward the neutral position. The frame 20 is movable with respect to the subject surface 12 within a predetermined plane. 2 permanent magnets on the rod 16
2 is fixed, and the coil 24 is fixed to the inner surface of the frame 20 which faces this. Permanent magnet 22 and coil 2
4 forms a linear motor 26, and electric power is supplied from a motor driver 28. Coil 2 of frame 20
The portion where 4 is arranged is preferably made of a soft magnetic material having a low magnetic resistance. This improves the efficiency of the linear motor 26.

At the other end of the rod 16 is a moving electrode 3
0 is fixed, and the fixed electrode 32 is fixed to the inner surface of the frame 20 facing the fixed electrode. These electrodes 30, 3
The capacitance between the two is the rod 16 or the objective electrode 14
It changes depending on the position of the rod in the axial direction. The displacement of the objective electrode 14 is calculated by the objective electrode displacement calculation unit 34 based on this capacitance. On the other hand, the objective electrode 14 and the subject surface 1
The gap with respect to 2 is calculated by the gap calculator 36. The motor driver 28 drives the linear motor 26 based on the output of the gap calculator 36 so that the gap matches the predetermined gap instruction value S1. The displacement of the objective electrode 14 due to this driving is calculated by the objective electrode displacement calculator 34 as described above. Therefore, the distance of the subject surface 12 with respect to the frame 20 is calculated by the distance calculator 38 as the sum of the calculated values of the objective electrode displacement calculator 34 and the gap calculator 36. The shape of the surface of the subject can be measured by moving the frame 20 in a predetermined plane, for example, a plane orthogonal to the axis of the rod 16 and calculating the distance at a plurality of points.

FIG. 2 is a diagram showing details of the objective electrode 14. A substantially disk-shaped partial electrode 40 is arranged at the tip of the rod 16 via an insulating material. A substantially annular partial electrode 42 is disposed outside the partial electrode 40 with an insulating support material 44 interposed therebetween. Lead wires 46 and 48 are connected to the partial electrodes 40 and 42, respectively. The objective electrode 14 includes these partial electrodes 40, 42.
And an insulating support material 44. Partial electrodes 40, 4
2, a capacitor is formed using the surface 12 of the subject, which is a conductor, as an intermediary electrode. This capacitance is inversely proportional to the gap between the objective electrode 14 and the subject surface 12, more specifically, the average gap in the area A when the objective electrode 14 is projected onto the subject surface 12. Therefore, by measuring this capacitance, the gap between the objective electrode 14 and the subject surface 12 can be measured.

3 and 4 are views showing the details of the support structure 18. As shown in FIG. The rod 16 has a substantially disc-shaped outer flange 50.
Is provided. Outer periphery of outer flange 50 and frame 2
A predetermined distance is provided between the inner wall and the inner wall of 0. Inside the frame 20, an annular plate-shaped inner flange 52 is provided. The rod 16 penetrates through a hole provided at the center of the inner flange 52 with a gap. Between the two flanges 50 and 52, four support legs 54 are provided at equal intervals in the circumferential direction. The support leg 54 has coupling portions 56 and 58 that are coupled to the flanges 50 and 52 at both ends,
It includes two plate-shaped members (plates) 60, 62 and three elastic hinges 64, 66, 68 connecting them. The plates 60 and 62 are relatively thin in the radial direction of the rod 16 and have a plate shape having a width in a plane orthogonal to the axis of the rod 16 in the direction orthogonal to the radial direction (hereinafter, circumferential tangential direction). It is a member. The plates 60 and 62 are arranged so that the normal line on the center line in the rod direction intersects the axis of the rod. Coupling portions 56 and 58 and elastic hinge 6
4, 66 and 68 have a width substantially equal to that of the plates 60 and 62, and the elastic hinges 64, 66 and 68 are thin in the thickness direction. Further, these members are integrally formed and bent at the elastic hinges 64, 66, 68. 3 and 4, the left half of the center line is the support leg 5
4 shows the expanded state, and the right half shows the contracted state. Further, FIG. 4 is a cross-sectional view taken along the line BB shown in FIG.

The elastic hinges 64, 66, 68 are wide in the circumferential tangential direction, and as a result, the bending motion of the support leg 54 is restricted within the plane including the axis of the rod 16. By providing three or more support legs 54, the rod 16 and the frame 20
Relative movement of the rod 16 can be restricted only in the axial direction of the rod 16. Further, by providing the two support structures 18 in the axial direction of the rod 16, the inclination of the rod 16 can be sufficiently regulated. In addition, by appropriately selecting the shape of the support leg 54, the position of the rod 16 can be set to the substantially central position of the movable range in the initial state. The support leg 54 can be formed as an integral molding material by precision casting or the like. Further, the rod 16 can be supported even if the support legs 54 are three legs.

Incidentally, the rod 16 of each of these supporting legs 54
It is preferable that the support characteristics of the above have less variation.

FIG. 5 is a diagram showing details of the movable electrode 30 and the fixed electrode 32 for measuring the relative displacement between the rod 16 and the frame 20. Two electrodes 3 due to relative displacement
The opposing areas of 0 and 32 change, and the capacitance between the electrodes changes. Based on this capacitance change, the objective electrode displacement calculation unit 34
Thus, the relative displacement of the rod 16, that is, the objective electrode 14 with respect to the frame 20 is calculated. The objective electrode 14 is
Since the average gap in the region A is measured as described above, the larger the electrode area, the lower the resolution in the direction along the surface of the subject. Therefore, the electrode area of the objective electrode 14 cannot be increased and the measurement range is narrowed. On the other hand, the movable electrode 30 and the fixed electrode 32 are
There is no restriction on the area like the above-mentioned objective electrode 14,
Compared with the objective electrode 14, a large area can be taken. Therefore, the relative displacement of the rod 16 with respect to the frame 20 can be measured in a relatively wide range.

FIG. 6 shows another specific example of the movable electrode and the fixed electrode. A plurality of disk-shaped moving electrodes 70 are arranged on the rod 16 in the axial direction. These moving electrodes are electrically connected to each other by a connecting line 72. Inside the frame 20, a fixed electrode 74 having a substantially annular plate shape is
The movable electrodes 70 are arranged so as to face each other. Further, the rod 16 and the connecting wire 72 pass through the hole at the center of the fixed electrode 74 with a predetermined gap. The fixed electrodes 74 are electrically connected to each other by a connecting wire 76. The relative displacement of the rod 16 with respect to the frame 20 changes the distance between the moving electrode 70 and the fixed electrode 74, and changes the capacitance between these electrodes. By this change, the relative displacement of the rod 16 can be measured. In the case of this example, by arranging the movable electrode 70 and the fixed electrode 74 in multiple layers, the electrode area can be expanded and a wider measurement range can be obtained.

FIG. 7 shows still another specific example of the movable electrode and the fixed electrode. As compared with the example shown in FIG. 6, the diameter of the frame 78 in which the electrodes are arranged is larger, and the outer diameters of the plurality of moving electrodes 80 and the fixed electrode 84 are larger accordingly. These electrodes 80 and 84 are connected by connection lines 82 and 86, respectively. Similar to the case of FIG. 6, the moving electrode 8 generated by the relative displacement of the rod 16
A change in the distance between 0 and the fixed electrode 84 causes a change in capacitance, from which the relative displacement can be calculated. Since it is necessary to avoid electrostatic coupling with the objective electrode 14 in the vicinity of the objective electrode 14, the moving electrode 30 and the fixed electrode 32 for measuring the relative displacement between the frame 20 and the objective electrode 14 cannot be arranged. A large structure for measuring the relative displacement between the frame 20 and the objective electrode 14 via the rod 16 can be arranged at a position sufficiently separated from the objective electrode 14. In this example, the diameter of the frame 78 at a position distant from the objective electrode is increased to increase the electrode area and enable measurement in a wider range.

FIG. 8 and FIG. 9 show another example of arrangement of the movable electrode and the fixed electrode. FIG. 8 shows an example of a parallel plate moving electrode 88 and a fixed electrode 90. The moving electrode 88 moves integrally with the rod and the fixed electrode 90 moves to the frame in the same manner as the structure of the electrodes described above. It is fixed. FIG. 9 shows an example of a concentric cylindrical moving electrode 92 and a fixed electrode 94. Also in this case, the moving electrode 92 moves integrally with the rod, and the fixed electrode 94 is fixed to the frame. The electrode configurations shown in FIGS. 8 and 9 are for detecting the relative displacement by the displacement of the electrodes facing each other due to the relative displacement of the rod with respect to the frame and the resulting capacitance change. .

Next, the shape measurement of the surface of the subject will be described. The frame 20 of the distance measuring device 10 is fixed to a robot hand or the like. The median value of the measurement range of the distance measuring device 10 is input to the motor driver 28 as the gap instruction value S1. By the robot hand, the objective electrode 14 of the distance measuring device 10 is arranged at a distance corresponding to the gap indicating signal S1 from the subject surface 12. Then, the distance measuring device 10
Are moved along a predetermined plane, preferably along a plane substantially parallel to the subject surface 12. The gap calculator 36 outputs a value according to the gap between the objective electrode 14 and the surface 12 of the subject. This output value is fed back to the motor driver 28, and the motor driver 28 drives the linear motor 26 so as to maintain the gap instruction value S1. This drive amount,
That is, the objective electrode displacement calculator 34 outputs a value according to the amount of movement of the rod 16 with respect to the frame 20. The distance to the object surface 12 with respect to the plane that moves the distance measuring device 10 is the total of the displacements and gaps calculated by the objective electrode displacement calculation unit 34 and the gap calculation unit 36, and this is calculated by the distance calculation unit 38. . If the output of the distance calculation unit 38 is obtained at a plurality of points on the subject surface 12, the shape of the subject surface can be obtained.

As described above, since the gap between the objective electrode 14 and the subject surface 12 is feedback-controlled by the linear motor 26, the gap can be maintained within the measurement range of the objective electrode 14. Further, since the movable electrode and the fixed electrode can be configured to have a larger area than the objective electrode, a wider measurement range can be realized. In addition, even if the gap between the objective electrode 14 and the surface 12 of the subject changes rapidly with the movement of the distance measuring device 10 along the surface 12 of the subject, even if the feedback of the linear motor cannot catch up with the objective, The distance detected by the electrode 14, that is, the sum of the output of the gap calculation unit 36 and the relative displacement of the frame 20 and the rod 16, that is, the output of the objective electrode displacement calculation unit 34, correctly represents the distance to the subject surface 12. . That is, the output of the distance measuring device 10 follows the surface of the subject well.

FIG. 10 shows a schematic configuration of another embodiment of the present invention. The same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted. The distance measuring device 100 of this embodiment is different from the above-described device 10 in the structure of the support structure. In this embodiment, a static pressure air bearing is adopted as the support structure 112. Air pads 114 are arranged so as to surround the periphery of the rod 16 at two locations apart from each other in the axial direction of the rod 16. Air is supplied to the air pad 114 from an external air pump (not shown), and the air pad 114 is configured to send out the air supplied to the gap between the air pad 114 and the rod 16. The air sent into this narrow gap functions to support the rod 16 in the radial direction.
In the case of such an air bearing, since there is no function of restricting the movement in the axial direction, in the case of the present embodiment, this function is performed by the linear motor 26.

In the present embodiment, the air pad 114
The air outlets from are open over the entire circumference in a plane orthogonal to the rod 16, but the air outlets may be evenly arranged in the orthogonal plane. Further, in this embodiment, two sets of static pressure air bearings are adopted, but three or more sets may be used. Further, the positions of the air outlets of the air pads 114 of each set in the rod 16 direction do not necessarily have to be the same.

Furthermore, in the present embodiment, the rod 16 has a circular cross section, but it may be a polygon such as a triangle or a quadrangle, and air pads facing each side may be provided. By doing so, in addition to the rod supporting function, a rotation preventing function can be added.
In addition to the radial bearing shown in the present embodiment, a static pressure air bearing for rotation prevention may be provided.

The static pressure air bearing has been described above.
The working gas may be a gas other than air.

Since the support structure is a static pressure air bearing, the movable range of the rod in the axial direction can be widened. Further, since the rigidity in the direction orthogonal to the axis is also high, stable measurement is possible.

It is also possible to change the configurations of the movable electrode and the fixed electrode shown in the above embodiment. In addition, a linear scale with the necessary accuracy for measuring the relative displacement of the rod,
An optical wavelength interferometer or the like can also be used. Also,
The means for driving the objective electrode so that the gap with the subject surface is constant is not limited to a linear motor, but other driving means such as a means for converting the rotation of a normal motor into a linear motion by a rack and pinion mechanism. Can be used. Further, as for the support structure, it is possible to adopt various configurations that restrict the movement of the rod 16 in the direction orthogonal to the axis and allow the movement in the axial direction.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of the present embodiment.

FIG. 2 is a diagram showing a configuration of an objective electrode.

FIG. 3 is a diagram showing a configuration of a support structure.

FIG. 4 is a diagram showing a configuration of a support structure, which is taken along line B- of FIG.
It is a B line sectional view.

FIG. 5 is a diagram showing a configuration of a movable electrode and a fixed electrode for measuring relative displacement of a rod with respect to a frame.

FIG. 6 is a diagram showing another configuration of a moving electrode and a fixed electrode.

FIG. 7 is a diagram showing still another configuration of the movable electrode and the fixed electrode.

FIG. 8 is a diagram showing still another configuration of the movable electrode and the fixed electrode.

FIG. 9 is a diagram showing still another configuration of the moving electrode and the fixed electrode.

FIG. 10 is a diagram showing a schematic configuration of another embodiment.

[Explanation of reference numerals] 10,100 distance measuring device, 12 subject surface, 14
Objective electrode, 16 rod, 18 support structure, 20 frame, 26 linear motor, 28 motor driver,
30 moving electrode, 32 fixed electrode, 34 objective electrode displacement calculator, 36 gap calculator, 38 distance calculator, 50 outer flange, 52 inner flange, 54 support leg, 60, 62
Plate, 64, 66, 68 elastic hinge, 112
Support structure (static pressure gas bearing).

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-50-98864 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B ^7/ 00-7/34 102 G01B 21 / 00

Claims (12)

(57) [Claims] 1. A frame, an objective electrode disposed with a gap from the subject surface, and the objective electrode supported to the frame such that the gap with the subject surface is within a predetermined range. Objective electrode supporting means, objective electrode displacement detecting means for detecting displacement of the objective electrode with respect to the frame, gap detecting means for detecting a gap between the objective electrode and the subject surface based on capacitance, and the objective electrode displacement A distance measuring device that calculates a distance from a predetermined point on the frame to the surface of the subject based on the gap. In the distance measuring apparatus according to claim 1, wherein the objective electrode support means, the controlled based on the detected value of the gap detection means, the objective electrode so that the detected value becomes a predetermined range A distance measuring device having driving means for driving the. 3. The distance measuring device according to claim 1 or 2, wherein the objective electrode support means has a biasing means for biasing the objective electrode toward a neutral position. 4. The distance measuring device according to claim 1, wherein the objective electrode supporting means holds the objective electrode at one end, is arranged in a substantially vertical direction on the surface of the subject, and is movable in this direction. A rod, a linear motor including a permanent magnet fixed to the rod and a coil fixed to the frame, a support mechanism that movably supports the rod with respect to the frame, and the detected objective electrode A motor drive unit that controls the linear motor based on a gap on the surface of the subject,
Distance measuring device. 5. The distance measuring device according to claim 4, wherein the frame surrounds at least a part of the rod,
A distance measuring device comprising: a tubular member disposed substantially coaxially with the rod, wherein the coil is disposed on the tubular member, and the support mechanism is disposed between the rod and the tubular member. 6. The distance measuring device according to claim 4 or 5, wherein the objective electrode displacement detecting means includes an electrode fixed to the frame and an electrode fixed to the rod, and Along with this, a distance measuring device that detects the displacement of the objective electrode by detecting the change in the distance between the two types of electrodes. 7. The distance measuring device according to claim 4, wherein the objective electrode displacement detecting means includes an electrode fixed to the frame and an electrode fixed to the rod, and Along with this, a distance measuring device that detects the displacement of the objective electrode by detecting the change in the area of the facing portion of the two types of electrodes. 8. The distance measuring device according to claim 1 or 4, wherein the objective electrode displacement detecting means is a scale that moves in association with the displacement of the objective electrode, and a scale that is fixed and passes on the frame side. And a graduation detection unit for monitoring the distance. 9. The distance measuring device according to claim 1, wherein the objective electrode displacement detecting means is a laser interferometer. 10. The distance measuring device according to claim 5, further comprising an outer flange projecting outward from the rod and an inner flange projecting inside the tubular member, wherein the support mechanism is Two plates arranged in series between the inner and outer flanges and the two plates are mutually bendable in a plane including the axis of the rod, and regulate bending outside the plane. And a distance measuring device including at least three support legs including the two plates, one plate and an outer flange, and an elastic hinge arranged between the other plate and the inner flange. 11. The distance measuring device according to claim 4 or 5, wherein the support mechanism is a static pressure gas bearing. 12. The distance measuring device according to claim 1, means for moving the frame within a predetermined plane relative to the surface of the subject, and a plurality of movements of the frame. And a surface shape calculating unit that calculates the shape of the surface of the subject based on the measurement value of the distance measuring apparatus at the location.